Hydraulic fracturing aims at creating an additional level or permeability and to increase downhole gas or oil production surface areas. Indeed, low permeability, natural barriers of compact layers, impermeability due to drilling operations greatly limit hydrocarbon production. The gas or the oil contained in the unconventional reservoir cannot easily migrate from the rock to the production well without any stimulation.
The development of hydraulic fracturing has been dependent on the use of polymers to decrease surface pumping pressures, while maintaining the downhole fracturing pressure. This is called the drag reduction phenomenon.
Downhole fracturing requires pressures from 70 to 200 bars with very large volumes of water. Surface pumps work at 300-600 bars in average.
The addition of small doses of polymers, particularly of polyacrylamide type, enables to crack by strongly increasing the injected flow rate.
This currently requires injecting strong quantities of polymers in 10 or 15 sequences over 2 or 3 days. Such quantities may reach 10 tons for a fracturing operation.
For their ease of handling, polyacrylamides in the form of an emulsion have been used for years, with the following disadvantages:                Transport of emulsion quantities which are three times larger than the quantities of active materials;        Cost practically doubled with respect to powder polymers;        Injection of hydrocarbons and of surface-active agents, more and more questioned by environmental groups;        Tendency to thicken, despite the addition of antifreeze agents, in regions with very cold winters.        
Recently, for reasons of cost and efficiency, equipment has been developed to dissolve powder polymers on dedicated trucks (WO2010/020698). This applies, in particular, to PowderFrac™ trucks using a dispersion/grinding material, improving the suspending of such powders, the dissolution thereof, and the pumping towards the blender used to supply the piston pump for the fracturing. However, the equipment is expensive and requires a relatively specialized staff.
There thus currently is a need for polymer dosing and addition equipment having a lower cost and a simplified use.